问:为什么要把父类的析构函数定义成虚函数?
答:否则子类的析构函数可以未被调用,具体代码如下:

class A 
{
public:
 A(){TRACE("A()/n");};
 ~A(){TRACE("~A()/n");};
 
};class B : public A 
{
public:
 B(){TRACE("B()/n");};
 ~B(){TRACE("~B()/n");};
};void CEgDlg::OnButton1() 
{
 A * p = (A*)new B() ;
 delete p ; 
}

运行结果如下:

A()
B()
~A()